Brake pedal hard as a rock

[ryno_rx8]

Just picked up a 81 k10 for cheap as i knew it had issues. I have done lots of work to it and to the point of being able to drive it. I got it good to go and the brake pedal was rock hard and i had to stand on it to get it to stop the truck. First thought was booster. I replaced the booster and it is better kinda. When coming to a stop it works as it should but if i am in line of cars and need to move up slowly, the pedal goes back to being hard again. And also, if i pump the pedal, it gets hard and stays that way for a few. I have replaced one caliper. I haven't checked for an actual vacuum number but at the check valve it feels like there is plenty. Im not sure if it is related but my back brakes dont work, at all lol. When off the ground, the rear tires turn freely. Any help is appreciative. The truck does havea 6" lift but appears the lines were extended

 

[hinkv10]

Brake pedal feel is dictated by the rear brakes. Thats what I was always told while working as a service advisor. Get your rear brakes working and adjusted properly and go from there.

 

[smurph20]

HInky is right sounds like your hard peddle is because you are pushing against a blockage going to the rear brakes. Try bleeding them out first going from farthest from the pedal to closest. I bet when you crack that bleeder screw you will get a gush or air or really nasty fluid.

 

[ryno_rx8]

awesome guys, i will go from there are see what happens. My E-Brake cable has been cut if it makes a difference at all.

 

[smurph20]

Not really cause mine were cut or removed by previous owner.

 

[HotRodPC]

For a hard pedal, that seems to be a booster problem to me. So you've already replaced the booster. You say it FEELS LIKE there is plenty of vacuum at the check valve. Maybe the check vavle is bad and not letting the vacuum to the booster. See if you can bypass the check valve and go direct to the booster and see what happens. The check valve is not necessary. It's just an added safety feature so that if the motor shuts off, you should have some vacuum in reserve to stop the vehicle after the motor has shut off. That's it's only purpose.

It's also my thinkinging, back brakes not working would just mean a low pedal, but not a hard pedal. Granted, certainly stil possible for the hard pedal if you have a clog to the rear brakes somwhere. Are you sure it's not the proportioning valve? I'd be more suspect of these extended rear brake lines.